The present invention relates to loading of microchannel arrays, particularly to T or Cross (+) loading for microfluidic applications, and more particularly to an architecture for T or cross loading that enables a very dense layout of arrays of functionally identical shaped channels.
There are two main types of injection methods in microchannel electrophoresis. The first type is analogous to that used in discrete capillaries where the sample is introduced directly into the end of the microchannel, and there is one physical sample input port per channel. This has been used extensively, and is referred to as electrokinetic (ek) single port injection. The amount of sample actually injected into the column is a strong function of sample preparation, loading volume, input port shape and volume, exact loading placement, loading field and time, excess sample removal, holding time, etc. which may be hard to control.
The second type is a volumetric type of load called T load or Cross load, where the sample plug at the intersection of two microchannels is injected into the column. This type is exemplified by U.S. Pat. No. 5,900,130 issued May 4, 1999 to D. Benvegnu, et al. This load type is fundamentally controlled better by the geometry of the intersection, but now the number of input ports per channel has increased from one to three: sample, waste, and cathode. Ek effects may be present or used in the cross load, but the fundamental determinant of the amount of sample loaded and injected is the geometrical volume of the channel intersection, which is subsequently swept out by the running or separation field. The increased space required for additional input ports and the need to electrical bias all of them independently and initially fill them all with sieving media is geometrically and procedurally fraught with practical difficultiesxe2x80x94especially for very high density arrays.
The present invention addresses these geometrical and practical operational difficulties. The invention provides an architecture or layout composition which enables a very dense layout of arrays of functionally identical shaped channels. The invention also simultaneously enables efficient parallel shapes and biasing of input wells, waste wells, and bias wells at the input end of the separation columns.
It is an object of the present invention to provide a microchannel cross load array with dense parallel input.
A further object of the invention is to provide a unique architecture for microchannel arrays using T or Cross loading for electrophoresis.
Another object of the invention is to provide a T or Cross loading architecture which enables a very dense layout of arrays of functionally identical shaped channels.
Another object of the invention is to provide an architecture for microfluidic configurations that simultaneously enables efficient parallel shapes and parallel biasing of the input wells, waste wells, and bias wells at the input end of microchannel separation columns.
Other objects and advantages of the present invention will become apparent from the following description and accompanying drawings. The present invention involves an architecture or layout composition for microchannel T or Cross (+) loading to enable dense parallel input for electrophoresis or other injection and separation chemistry experiments that are preformed in microfluidic configurations. The present invention is an architecture for microchannel arrays using T or Cross loading which solves prior problems associated with very high density arrays. The invention provides a way to layout a dense array of similar cross loaders so that high channel densities result, and a minimum member of access holes is used by sharing holes in the multiple channel layout. This invention uses unique geometrical pattern shaped channels and packing of the layout, taking advantage of several mirror symmetries in the layout, and enables the use of the Cross loader, such as described in about-referenced U.S. Pat. No. 5,900,130, in dense practical arrays. Based on this layout, experiments show that for the large microchannel array fabrication technology that is currently known, over 1000 channels can be formed on one plate. The architecture of this invention utilizes the Cross loader of the above-referenced patent which consists of two intersecting microchannels (four arms), and provides a package or layout of building blocks in a practical way for a very high density planar integrated array.